The Association for Financial Markets in Europe (AFME) has asked Hanover to raise the organisation's profile across Europe, replacing incumbent M: Communications.
Hanover secured the brief, thought to be worth in excess of six figures annually, after a four-way pitch.
Formed in late 2009, the AFME lobbies national and international governmental institutions on behalf of the financial industry against what it deems to be unnecessary regulation.
The organisation is overseen by Simon Lewis, the ex-Vodafone and NatWest comms chief who served as Gordon Brown's official spokesman.
Hanover will assume its role in early April to coincide with the opening of AFME's Brussels office. Rob McIvor, AFME's comms director, confirmed Hanover's appointment and said the agency would provide 'strategic advice and act as a sounding board' for the firm.
He added that AFME had established itself in the UK, but needed to increase its presence and profile in legislative and regulatory circles in Europe.
Hanover director Laura Chisholm will lead the account.